How to add a range of separate images to VSE without merging them in one video strip?
Add images as usual strip and then use Separate Images to make each image as separate strip.

From manual:


  Y Converts the strip into multiple strips, one strip for each frame. Very useful for slide shows and other cases where you want to bring in a set on non-continuous images.


With strip selected press Y (or open Strip > Separate Images) and choose how long (in frames) each resulting strip should be.




Then you can grab resulting strips as desired.